1. Field of the Invention
This invention relates to a method and apparatus for mining and supporting the mine roof and more particularly to a method and apparatus for providing temporary roof support while the mining machine advances to form a second unsupported portion of the mine roof and for providing temporary roof support adjacent the location where permanent roof supports are to be installed in the second unsupported portion of the mine roof.
2. Description of the Prior Art
In underground mining especially the mining of coal the length of unsupported roof formed during the mining operation is limited to a preselected length as for example twenty feet. It is necessary after twenty foot of unsupported roof is formed to withdraw the mining machine from the entry to a cross-heading and thereafter move a bolting machine beneath the unsupported portion of the roof and provide permanent support by first drilling vertical holes in the roof and anchoring roof supports in the predrilled holes. Thus with the present practice the continuous penetration of the mining machine is limited to the preselected length of unsupported roof.
Further, in conventional mining the self-propelled roof drill and bolter sets rows of bolts inby of the last row of bolts. The setting of the row of bolts requires the self-propelled drill and bolter to first drill vertical holes in the rows and thereafter to anchor roof bolts therein. The personnel operating the roof drill and bolter are frequently working beneath a portion of the unsupported roof. There is a need for a method of temporarily supporting unsupported portions of the roof so that the continuous miner can advance a distance greater than the predetermined distance now limited by the unsupported roof and further a method of temporarily supporting the roof where the roof drill and bolter personnel are working without exposing the personnel to the hazards of unsupported roof and thus provide a roof section that is supported in substantially the same manner as by the permanent roof bolts while the roof bolts are being installed.
In order to provide some protection for the personnel operating the roof drill and bolter it has been the practice in the past to manually set several temporary jacks or posts inby of the location where the rows of bolts are to be set to thus reduce the danger of roof fall for the personnel setting the line of roof bolts. The manual placement of the temporary jacks is not satisfactory because it exposes the personnel setting the jacks to the same hazards as the personnal operating the roof drill and bolter under unsupported roof.